The Icelandic Laki Volcanic Tephra Layer in the Lomonosovfonna Ice Core, Svalbard

The Icelandic Laki volcanic tephra layer in the Lomonosovfonna ice core, Svalbard

Teija Kekonen, John Moore, Paavo Perämäki & Tõnu Martma

The largest sulphuric acid event revealed in an ice core from the Lomono- sovfonna ice cap, Svalbard, is associated with the densest concentration of microparticles in the ice core at 66.99 m depth. Electron microscope analysis of a volcanic ash particle shows it has the same chemical composition as reported for debris from the eruption of Iceland’s Laki fi ssure in 1783 and confi rms the identifi cation of the tephra. Most of the particles in the deposit are not ash, but are common sand particles carried aloft during the eruption event and deposited relatively nearby and downwind of the long-lasting eruption. The tephra layer was found 10 - 20 cm deeper than high sulphate concentrations, so it can be inferred that tephra arrived to Lomonosovfonna about 6 - 12 months earlier than gaseous sulphuric acid precipitation. The sulphuric acid spike has a signifi cant cooling impact recorded in the oxygen isotope profi le from the core, which corresponds to a sudden drop in temperature of about 2 °C which took several years to recover to previous levels. These data are the fi rst particle analyses of Laki tephra from Svalbard and confi rm the identifi cation of the large acidic signal seen in other ice cores from the region. They also confi rm the very large impact that this Icelandic eruption, specifi cally the sulphuric acid rather than ash, had on regional temperatures.

T. Kekonen, University of Oulu, Box 3000, FI-90014 University of Oulu, Finland and Arctic Centre, Uni- versity of Lapland, Box 122, FI-96101 Rovaniemi, Finland, teija.kekonen@oulu.ﬁ ; J. Moore, Arctic Centre, University of Lapland, Box 122, FI-96101 Rovaniemi, Finland; P. Perämäki, Dept. of Chemistry, University of Oulu, Box 3000, FI-90014 University of Oulu, Finland; T. Martma, Institute of Geology, Tallinn Univer- sity of Technology, Estonia pst 7, EE-10143 Tallinn, Estonia.

Volcanic ash particles are commonly detect- particle size. In addition to volcanic ash particles, ed from ice cores because of their importance tephra contains other larger sand and rock par- for dating (e.g. Grönvold et al. 1995; Zielinski ticles. Ash and other small particles can travel et al. 1997). Volcanic eruptions usually produce long distances, but bigger sand particles are much large volumes of SO2 gas, dust, lava, ash and rock heavier than ash and are deposited much closer (Thordarson et al. 2001). Volcanic material can to the eruption site. Volcanic ash is the smallest travel high into the atmosphere and mix with air tephra fragment (< 2 mm) composed of silicon, masses, which can spread very widely. This mate- aluminium, iron, calcium, magnesium, sodium rial is eventually scavenged in precipitation, or and other trace elements. Each volcanic eruption deposited dry in very arid regions. produces volcanic ash particles with a specifi c Volcanic tephra includes all rock and lava par- signature in these elements, thereby producing a ticles that are erupted into the air, regardless of chemical fi ngerprint by which it can be identifi ed

Kekonen et al. 2005: Polar Research 24(1–2), 33–40 33 al. 1994; Zielinski et al. 1994; Thordarson et al. 1996; Watanabe et al. 2001; Thordarson & Self 2003). In this work we have analysed samples close to a major sulphate peak in the ice core and found a particle-rich layer at a depth of 66.99 m using SEM-EDS. This is the ﬁ rst published result relat- ing to the tephra layer and volcanic ash particle from the Laki eruption located in Svalbard gla- ciers.

Study site and methods

The 121 m long ice core was recovered with an electromechanical drill from the summit of the Lomonosovfonna ice cap (1255 m a.s.l.), on the island of Spitsbergen, Svalbard, in 1997 (Fig. 1) (Isaksson et al. 2001). Total ice depth from radar sounding was 123 m, and the site is close to the highest point of the ice cap with roughly radial ice fl ow. The ice core represents an approximately 800 year period. The time scale of the core was based on an ice layer thinning model (Nye 1963) tied with the known dates of prominent reference horizons (1963 radioactive layer and 1783 Laki Fig 1. Map showing Svalbard and Iceland and the inferred volcanic sulphate layer and volcanic ash particle; plume direction of the westerly jet stream on 10 June 1783. Transport paths are based on the data of Thordarson & Self see Kekonen et al. [2005] for details). The accu- (2003) and Fiacco et al. (1994). mulation rate for the 1997–1963 period is 0.41 m water equivalent per year and a somewhat lower value of 0.31 m w.e. per year for the period 1963– (e.g. Palais et al. 1992; Grönvold et al. 1995; Zie- 1783. The model age profi le can be independently linski et al. 1997; Zielinski et al. 1998). checked by comparison with automated seasonal The eruption of Iceland’s Laki fracture in 1783 cycle counting in stable isotopes and ions down to was one of largest basaltic fi ssure eruptions in 81 m (Pohjola et al. 2002). The model age at 81 m recorded history. The volume of aerosols inject- depth is 1705, while the cycle counting method ed into the atmosphere by the eruption was one gives a date of 1715. There is a thus a discrepan- of the greatest atmospheric pollution events over cy of 10 years in about 75 years between the Laki Europe during historic times (Thordarson & Self horizon and the limit of cycle counting. Howev- 2003). The Laki volcanic eruption lasted for eight er, the cycle counting method will always tend to months (June 1783 to February 1784) and pro- miss a fraction of low accumulation rate years duced one of the largest recorded basaltic lava due to the resolution of the data and isotope dif- fl ows in Iceland. The sulphuric and, especially, fusion effects, so a good model dating should be the hydrofl uoric acid produced by the eruption more reliable (on average) than cycle counting. were responsible for the deaths of more than half The current annual temperature range is from the animals on Iceland (Thordarson & Hoskulds- 0 °C to about –40 °C. Any summer meltwater son 2002). There were also widespread effects is refrozen mostly within the previous winter’s in the Northern Hemisphere, including cooling snow, and the remainder within the next two or (Thordarson & Hoskuldsson 2002; Highwood & three lower annual layers. Although percolation Stevenson 2003; Thordarson & Self 2003). can be up to eight years in the warmest years in A strong sulphate acid signal corresponding the 20th century, it was much reduced during to an age of 1783–84 has been reported in many the Little Ice Age (Kekonen et al. 2005). Vari- ice cores from Greenland and Svalbard (Fiacco et ous statistical analytical methods (see Kekonen

34 The Laki tephra layer in the Lomonosovfonna ice core et al. 2005; Moore et al. 2005) show that chemi- measure the chemical composition of all the par- cal and isotopic stratigraphy are suffi ciently well ticles present on a 271 × 191 mm subsections of preserved that signifi cant decadal-scale periodic- the 490 mm2 fi lter membrane. In total we ana- ities can be found, annual layers can be count- lysed 2063 particles in 44 different subsections of ed for about 300 years, and changes in chemical the same fi lter membrane. composition related to changes in climate are far more signifi cant than changes in chemical composition in ice layers subject to various degrees Results and discussion of percolation. The core was transported and stored in a frozen There are no visible dust or tephra bands in the state (–22 °C). The whole ice core was cut into ice core, but particles were sought at many depths 5 cm sections and the outer parts of the samples using the method described above. Enormous were removed in a cold room under a laminar amounts of tephra (approximately half a mil- fl ow hood. For particle analyses, selected sam- lion particles) were detected on the 66.99 - 67.04 ples were melted and fi ltered under a laminar fl ow m depth fi lter membrane. The subsection typical- hood. The 10 - 20 ml of meltwater was fi ltered ly contained 30 - 100 particles, most commonly just after melting with Nuclepore polycarbonate 50. (For comparison, at other depths a subsection membranes (25 mm diameter and 0.2 mm pore usually contained less than 10 particles.) This is size) using a vacuum fi lter system. Each sample the only depth where tephra were found close to was fi ltered through separate fi lter membranes. a high sulphate and acidity peak (66.69 - 66.89 m) Filter membranes were glued onto the stubs using (Fig. 2). Most of the tephra were small sand par- carbon-coated double-sided tape and coated with ticles of basaltic composition (Fig. 3). The SiO2 a thin fi lm of carbon. Samples were analysed for composition is approximately same as in parti- major elements using a Jeol JMS-6400 scanning cles originating from Laki eruption as reported electron microscope combined with a Link ISIS in the literature (see references in Table 1). While and INCA energy dispersive spectrometer. An the automated analyses in Fig. 3 do not give very acceleration voltage of 15 kV and a beam current exact chemical compositions due to the nature of 1.2 nA were used for the SEM-EDS (scanning of the particle morphology, the large numbers of electron microscope energy dispersive spectrom- analyses give a statistical view of tephra com- eter) analysis with the sample distance of 15 mm. position relative to the composition of the Laki Acidity was measured using a Radiometer Copen- tephra. hagen PHM 205 pH meter and XC 161 combined A volcanic ash particle (that is, an amorphous pH electrode. For acidity measurements, samples glassy shard indicative of volcanic eruption activ- were melted under nitrogen atmosphere to pre- ity) was found amongst the many sand particles vent carbon dioxide dissolution. (Fig. 4) and was analysed in detail using a spot + + + 2+ 2+ – All the ions (Na , K , NH4 , Mg , Ca , Cl , analyser at 40 points on the particle. Comparison – 2– – NO3 , SO4 , CH3SO3 ) were analysed over the of the chemical composition of the particle with whole core in 5 - 10 cm resolution using a Dionex the composition of tephra from known eruptions ion chromatograph with conductivity detector and indicates that particles found in the Lomonosov- suppressor housed in a clean laboratory. Details fonna ice core originate from the volcanic erup- for ion chromatography analyses are described by tion of Laki in 1783 (Table 1). The tephra (includ- Kekonen et al. (2002) and Kekonen et al. (2004). ing sand and ash) was ejected into the atmosphere δ18O was determined using a Finnigan-MAT by the fi ssure eruption mechanism that is typifi ed Delta-E mass spectrometer (Isaksson et al. 2001). by the Laki eruption (Fiacco et al. 1994). Atmos- Results are measured against laboratory inter- pheric transport directed the Laki aerosol plume nal standard water, which has been calibrated on fi rst to the east and the north-east (Thordarson & the V-SMOW/SLAP scale using the international Self 2003) (Fig. 1). Since Svalbard is rather near reference materials V-SMOW (Vienna Standard to Iceland—less than 2000 km—and general- Mean Oceanic Water) and SLAP (Standard Light ly downwind of it, many heavy sand particles in Antarctic Precipitation) from the International addition to ash particles are observed in the core. Atomic Energy Agency. Reproducibility of repli- The volcanic tephra layer is about 10 - 20 cm cate analyses is generally better than ± 0.1 ‰. deeper than the high sulphate concentration and We used an automated particle analyser to acidity peaks (seen between 66.69 and 66.89 m)

Kekonen et al. 2005: Polar Research 24(1–2), 33–40 35 Fig. 2. Sulphate (thick line) concentrations and acidity (thin line) near the Laki peak. The tephra layer is marked by the thick black vertical line.

(Fig. 2). At this depth (66 - 67 m), the 5 cm sample fonna ice cap lasted for 9 - 15 months. ECM anal- resolution roughly corresponds to few months of yses of Greenland ice cores (Clausen et al. 1997) time. This indicates that the volcanic tephra was indicate that the fallout from the Laki eruption carried to Lomonosovfonna ice cap about 3 - 9 lasted 1.0 and 1.6 years there. months before the sulphuric acid started to pre- After the main sulphate concentration and acid- cipitate on the glacier, and 6 - 12 months before ity peaks, a smaller peak can also be observed the main sulphuric acid precipitation occurred. (Figs. 2, 5). Thordarson et al. (1996) reported Sulphuric acid precipitation on the Lomonosv- that high discharge basaltic eruptions, such as

Table 1. Mean value and standard deviation for the 40 spot analysis of volcanic ash particle (Fig. 4) compared to other Laki particles. “Ref. 1” is the composition of the glass phase of the Laki eruption. An average of six samples and ten glass grains were analysed in each sample (. Grönvold, pers. comm. 2002). Refs. 2 and 3 are the composition of Laki tephra (T. Thordarson, unpubl. data; Fiacco et al. 1994). Ref. 4 is the composition of particles from ﬁ lter paper collected from the GIPS2 ice core (Fiacco et al. 1994). Ref. 5 is the major element composition of Laki glass (Thordarson et al. 1996). The number of analyses is shown in the last column (n).

wt. % Na2OMgOAl2O3 SiO2 SO3 K2OCaOTiO2 MnO FeO n Mean 2.81 6.59 13.16 50.64 0.45 0.18 10.20 2.07 0.03 13.85 40 SD 0.50 0.65 0.56 1.09 0.22 0.12 1.17 0.23 0.09 1.50 Ref. 1 2.61 5.32 12.70 49.10 0.47 10.10 2.96 0.24 13.70 Ref. 2 2.78 5.40 13.26 49.97 0.44 9.90 3.02 0.21 14.08 18 SD 0.11 0.02 0.02 0.07 0.01 0.03 0.01 0.00 0.05 Ref. 3 1.83 5.48 12.96 54.47 0.50 9.23 2.84 12.69 3 SD 0.18 0.47 1.56 1.05 0.01 0.59 0.35 1.01 Ref. 4 1.26 4.81 13.05 52.26 0.69 10.41 2.88 14.64 5 SD 0.52 0.65 0.95 2.45 0.25 0.90 0.34 2.59 Ref. 5 2.84 5.78 13.05 49.68 0.42 10.45 2.96 0.22 13.78 21 SD 0.12 0.30 0.48 0.36 0.05 0.28 0.17 0.03 0.61

36 The Laki tephra layer in the Lomonosovfonna ice core Fig. 3. Chemical compositions of 2063 particles by automated analysis in 44 different subsections of the membrane ﬁ lter from a depth of 66.99 m. The box shows the chemical composition of Laki volcanic ash particles from the literature cited in Table 1.

Laki, are able to loft huge quantities of gas to alti- tudes (including the troposphere and lower stratosphere) where the resulting aerosol can reside for 1 - 2 years (Stevenson et al. 2003). In Green- land ice cores high sulphate peaks are observed in spring, summer and autumn 1784, indicating that the increased atmospheric loading of SO2 lasted for about a year (Fiacco et al. 1994; Thordarson et al. 1996). The highest sulphate concentration observed in the Greenland ice cores is about 1300 µg L–1 (Fiacco et al. 1994), which is slightly lower than we observe in the Lomonosvfonna ice core (Fig. 2). The mean acidity of the Laki signal is 18 ± 8 µg L–1. Thordarson & Self (2003) estimat- ed the excess optical depth caused by the eruption relative to that due to the absolutely calibrated Krakatau aerosol cloud with a correction for the different geographic extent of the volcanic clouds. Fig. 4. A volcanic ash particle from a depth of 66.99 m. The method requires only the mean amplitude of the acidity of the Laki peak in Greenland ice cores, and produces an excess optical depth of 0.8 ± 0.4. The impact of the large acidity pulse on Europe- Applying the same procedure to the Lomonosov- an temperatures has been well documented using fonna acidity record results in an excess optical various historical and proxy archives (Thordar- depth of 0.9 ± 0.4, which is in excellent agreement son & Self 2003). The impact on the Lomonos- with Thordarson & Self (2003). Clausen et al. ovfonna δ18O isotopic temperature proxy (Isaks- (1997) report acidic fallout in central and south- son et al. 2003) can be seen in Fig. 5. It is clear ern Greenland ice cores (147 and 177 kg km–2, that there is an immediate drop in δ18O follow- respectively). This compares with a fallout pre- ing the acid deposition rather than the ash fall- served in the Lomonosovfonna ice core of 390 kg out recorded by the tephra layer deposit. There km–2. This much larger fallout is a consequence is a 0.8 ‰ dip in 3-year running means relative of Svalbard being virtually downwind of Iceland to 30-year running means in δ18O for the 3 years during the eruption, while southern and, especial- following the acidic fallout, and this represents ly, central Greenland were essentially upwind. the lowest value of δ18O between 1400 and the

Kekonen et al. 2005: Polar Research 24(1–2), 33–40 37 Fig. 5. Sulphate (thick line) concentrations and isotope δ18O value (thin line) as a proxy for temperature near the Laki sulphate peak. The tephra layer is marked by the thick black vertical line.

1820s, and may therefore be regarded as highly 1.3 °C, respectively, in the wider Northern Hemi- signifi cant. This is in contrast with the signal in sphere after the Laki eruption. the Greenland ice cores, where either a modest There are several reasons why the tempera- rise in δ18O or no change is seen immediately fol- ture drop in Svalbard may have been higher than lowing the eruption (Vinther et al. 2003). How- in mainland Europe. It is clear that recovery to ever, this apparent discrepancy may be explained more normal temperatures takes at least two to by the larger acidic fallout to the west of Iceland three years (Thordarson & Self 2003). Although over Europe and Svalbard, and the typical see- the Laki eruption probably did not eject aero- saw behaviour of the North Atlantic Oscillation, sol into the upper stratosphere (Stevenson et al. resulting in temperature anomalies of opposite 2003), where long residence times are possible, sign over Europe and Greenland, (e.g. Vinther et the long-lasting nature of the eruption helped al. 2003). to produce a persistent temperature depression, We can calibrate the δ18O–temperature relation- at least over much of Europe. The North Atlan- ship with borehole thermometry. Van de Wal et tic sea surface temperatures during the period al. (2002) analysed the borehole temperature pro- 1780–1820 were monitored by the British Admi- fi le, fi nding that temperatures in the 19th centu- ralty and are discussed by Bjerknes (1964): the ry were 2.4 °C colder than the 20th century. This ocean south of 40° N was up to 3 °C warmer than compares with a 0.8 ‰ difference in δ18O (Isaks- the present climate, while the northerly parts son et al. 2003) between the 19th and 20th centu- were 2 - 3 °C cooler. This condition would read- ries—virtually the same depression as caused by ily lead to increased sea ice cover in the Green- the Laki eruption. Thus we can estimate that the land, Iceland and Barents seas, providing a ready 3 year dip in δ18O corresponds to about a 2.4 °C positive feedback mechanism for a year or two. temperature fall. We could also use a calibra- Feedbacks with the large-scale atmospheric cir- tion of isotopes against instrumental temperature culation patterns similar to those found for more records. However, extrapolating the calibrations recent eruptions (Kirchner et al. 1999) may also to the colder pre-20th century period is unrelia- have enhanced the impact of the eruption. ble (e.g. von Storch et al. 2004), so we prefer to use the estimate based on the borehole temperature profi le. Highwood & Stevenson (2003) and Thordarson & Self (2003) observed in their cal- culations that temperature decreased 0.21 °C and

38 The Laki tephra layer in the Lomonosovfonna ice core Conclusions Isaksson, E., Hermanson, M., Hicks, S., Igarashi, M., Kami- yama, K., Moore, J. C., Motoyama, H., Muir, D., Pohjola, V., Vaikmäe, R. & van de Wal, R. 2003: Ice core from Sval- The insoluble fractions of ice core samples show bard—useful archives of past climate and pollution history. that during the 1783 Laki volcanic eruption mas- Phys. Chem. Earth 28, 1217–1228. sive amounts of tephra arrived to the Lomonos- Isaksson, E., Pohjola, V., Jauhiainen, T., Moore, J., Pinglot, J. ovfonna ice cap in Svalbard. The volcanic tephra F., Vaikmäe, R., van de Wal, R. S. W., Hagen, J. O., Ivask, J., Karlöf, L., Martma, T., Meijer, H. A. J., Mulvaney, R., layer includes large amounts of sand particles Thomassen, M. & van den Broeke, M. 2001: A new ice core which suggests that not only light ash particles record from Lomonosovfonna, Svalbard: viewing the data were well transported downwind from the erup- between 1920–1997 in relation to present climate and envi- tion site. The heavy particles would also have ronmental conditions. J. Glaciol. 47, 335–345. Kekonen, T., Moore, J., Mulvaney, R., Isaksson, E., Pohjo- been resistant to removal on the ice cap by wind. la, V. & van de Wal, R. S. W. 2002: An 800 year record of The tephra layer was found 10 - 20 cm deeper nitrate from the Lomonosovfonna ice core, Svalbard. Ann. than high sulphate concentrations and acidity Glaciol. 35, 261–265. and shows that tephra arrived to the ice cap 6 - 12 Kekonen, T., Moore, J., Perämäki, P., Mulvaney, R., Isaksson, months earlier than gaseous sulphur dioxide was E., Pohjola, V. & van de Wal, R. S. W. 2005: The 800 year long ion record from the Lomonosovfonna (Svalbard) ice rained out as sulphuric acid. The sulphuric acid core. J. Geophy. Res. 110(D7), 10.1029/2004JD005223. precipitation lasted 9 - 15 months. Analyses indi- Kekonen, T., Perämäki, P. & Moore, J. C. 2004: Compar- cate that the geochemical compositions of the ison of analytical results for chloride, sulfate and nitrate volcanic tephra are basaltic, and the geochemical obtained from adjacent ice core samples by two ion chro- matographic methods. J. Environ. Monit. 6, 147–152. signatures of an ash particle show derivation from Kirchner, I., Stenchikov, G., Graf, H.-F., Robock, A. & Antuna, the Icelandic Laki volcanic eruption in 1783. J. 1999: Climate model simulation of winter warming and summer cooling following the 1991 Mount Pinatubo volcanic eruption. J. Geophys. Res. 104(D16), 19039–19055. Moore, J. C., A. Grinsted, T., Kekonen & Pohjola, V. 2005: Separation of melting and environmental signals in an ice core with seasonal melt. Geophys. Res. Lett. doi:10.1029/ Acknowledgements.—The authors thank the Finnish Forest 2005GL023039 Research Institute Research Station in Rovaniemi for cold Nye, J. F. 1963: Correction factor for accumulation measured and clean room facilities and Aslak Grinsted for helpful anal- by the ice thickness of the annual layers in an ice sheet. J. yses. The drilling of the Lomonosovfonna 1997 ice core was Glaciol. 4, 785–788. fi nanced by the Norwegian Polar Institute and the Institute Palais, J. M., Germani, M. S. & Zielinski, G. A. 1992: Inter- for Marine and Atmospheric Research, Utrecht. The labora- hemispheric transport of volcanic ash from a 1259 A.D. vol- tory work presented here was funded by the Finnish Academy canic eruption to the Greenland and Antarctic ice sheets. Figare project. Elisabeth Isaksson, Veijo Pohjola, Roderik van Geophys. Res. Lett. 19, 801–804. de Wal and all the fi eld participants are also thanked. Pohjola, V. A., Martma, T., Meijer, H. A. J., Moore, J. C., Isaks- son, E., Vaikmäe, R. & van de Wal, R. S. W. 2002: Recon- struction of 300 years annual accumulation rates based on the record of stable isotopes of water from Lomonosovfon- References na, Svalbard. Ann. Glaciol. 35, 57–62. Stevenson, D. S., Johnson, C. E., Highwood, E. J., Gauci, V., Bjerknes, J. 1964: Atlantic air–sea interaction. Adv. Geophys. Collins, W. J. & Derwent, R. G. 2003: Atmospheric impact 10, 1–82. of the 1783–1784 Laki eruption. Part I: chemistry model- Clausen, H. B., Hammer, C. U., Hvidberg, C. S., Dahl-Jensen, ling. Atmos. Chem. Phys. 3, 487–507. D. & Steffensen, J. P. 1997: A comparison of the volcan- Thordarson, T. & Hoskuldsson, A. 2002: Classic geology in ic records over the past 4000 years from the Greenland Ice Europe. 3: Iceland. Herts, UK: Terra Publishing. Core Project and Dye 3 Greenland ice cores. J. Geophys. Thordarson, T., Miller, D. J., Larsen, G., Self, S. & Sigurdsson Res. 102(C12), 26707–26723. H. 2001: New estimates of sulphur degassing and atmos- Fiacco, R. J., Thordarson, T., Germani, M. S., Self, S., Palais, pheric mass-loading by the 934 AD Eldgjá eruption, Ice- J. M., Whitlow, S. & Grootes, P. M. 1994: Atmospheric aer- land. J. Volcan. Geotherm. Res. 108, 33–54. osol loading and transport due to the 1783–84 Laki erup- Thordarson, T. & Self, S. 2003: Atmospheric and environ- tion in Iceland, interpreted from ash particles and acidity in mental effects of the 1783–1784 Laki eruption: a review and the GISP2 ice core. Quat. Res. 42, 231–240. reassessment. J. Geophys. Res. 108(D1), 4011–4039. Grönvold, K., Óskarsson, N., Johnsen, S. J., Clausen, H. B., Thordarson, T., Self, S., Óskarsson, N. & Hulsebosch, T. Hammer, C. U., Bond, G. & Bard, E. 1995: Ash layer from 1996: Sulfur, chlorine, and fl uorine degassing and atmos- Iceland in the Greenland GRIP ice core correlatred with pheric loadings by the 1783–1784 AD Laki (Skaftár Fires) oceanic and land sediments. Earth Planet. Sci. Lett. 135, eruption in Iceland. Bull. Volcan. 58, 205–225. 149–155. van de Wal, R. S. W., Mulvaney, R., Isaksson, E., Moore, J. Highwood, E. J. & Stevenson, D. S. 2003: Atmospheric impact C., Pinglot, J.-F., Pohjola, V. & Thomassen, M. P. A. 2002: of the 1783–1784 Laki eruption. Part II: climatic effect of Reconstruction of the historical temperature trend from sulphate aerosol. Atmos. Chem. Phys. 3, 1177–1189. measurements in a medium-length bore hole on the Lono-

Kekonen et al. 2005: Polar Research 24(1–2), 33–40 39 mosovfonna Plateau, Svalbard. Ann. Glaciol. 35, 371–378. Res. Spec. Iss. 54, 227–242. Vinther, B. M., Johnsen, S. J., Andersen, K. K., Clausen, H. B. Zielinski, G. A., Fiacco, R. J., Mayewski, P. A., Meeker, L. D., & Hansen, A. W. 2003: NAO signal recorded in the stable Whitlow, S., Twickler, M. S., Germani, M. S., Endo, K. & isotopes of Greenland ice cores. Geophys. Res. Lett. 30, Yasui, M. 1994: Climatic impact of the A.D. 1783 Asama doi:10.1029/2002GL016193. (Japan) eruption was minimal: evidence from the GISP2 ice von Storch, H., Zorita, E., Jones, J. M., Dimitriev, Y., core. Geophys. Res. Lett. 21, 2365–2368. González-Rouco, F. & Tett, S. F. B. 2004: Reconstructing Zielinski, G. A. & Germani, M. S. 1998: New ice-core evi- past climate from noisy data. Science 306(5696), 10.1126/ dence challenges the 1620s BC age for the Santorini science.1096109. (Minoan) Eruption. J. Archaeol. Sci. 25, 279–289. Watanabe, O., Motoyama, H., Igarashi, M., Kamiyama, K., Zielinski, G. A., Mayewski, P. A., Meeker, L. D., Grönvold, Mat oba, S., Goto-Azuma, K., Narita, H. & Kameda, T. K., Germani, M. S., Whitlow, S., Twickler, M. S. & Taylor, 2001: Studies on climatic and environmental changes K. 1997: Volcanic aerosol records and tephrochronolo- during the last hundred years using ice cores from various gy of the Summit, Greenland, ice cores. J. Geophys. Res. sites in Nord aust landet, Svalbard. Mem. Natl. Inst. Polar 102(C12), 26 625–26 640.

40 The Laki tephra layer in the Lomonosovfonna ice core